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What is the difference between physical address and logical address?

Date: 17 Jan 2011   Group: Computers    Category: Hardware    Posted By: [Anonymous]   


What is the difference between physical address and logical address?


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Author: vinodh kumar kc    21 Jan 2011      Member Level: Silver     Points : 3  (Rs 3)    Voting Score: 0

Hi,

It is commonly asked question by all beginners of computer science also most people find it difficult to understand the thing.

Physical address

Physical address is the actual memory address which denotes a memory area in your storage device.

Logical address

The operating system or some other programs uses base addresses as a measure to find addresses. Here base address means starting address of a memory block. According to the program written the CPU generates a address.This address is added with the base address so that it forms the physical address.Here in this case the address generated by the CPU is called as Logical Address.

The address which is generated by the CPU which is added with base address to form th physical address is called as logical address

With Regards

K C Vinodh Kumar

Author: brijesh singh    22 Jan 2011      Member Level: Gold     Points : 2  (Rs 2)    Voting Score: 0

Hi,
Physical address refers to the address that comes with the device itself and that remains permanent for a device. It cannot be changed . For example the MAC(Medium Access Control) Address is a physical address. A particular machine will always have this address as long as it exists on the internet highway.

On the other hand , a logical address is the address that is given or assigned to a device which registers its presence on the internet highway. At a particular time this address will be unique for the device but it may change at some times in future.
IPv4 is an example of Logical Address.


Brijesh Singh
Gold, ISC




Author: Deepanker Srivastava    04 Feb 2011      Member Level: Silver     Points : 3  (Rs 3)    Voting Score: 0

Hello,

You can understand the difference between physical and logical address on the basis of following points:

1.Physical address is the address loaded in the memory address register whereas a logical address is the address generated by the CPU.

2.Logical address is also called as virtual address since it corresponds to a location in logical memory whereas physical address corresponds to a location in physical memory(most often it is RAM).

3.There is no direct real location that the logical address points.All logical addresses are always mapped to physical addresses.

4.The data is stored at physical address whereas logical address is only a virtual location in virtual memory.

With Regards,
Deepanker Srivastava.

Author: rajan j    04 Feb 2011      Member Level: Bronze     Points : 1    Voting Score: 0

physical=denote a memory area.and we can't change the present NIC card given by internic organization.
logical=we can changed for assinging ip address for clients

Author: Saheblal    06 Feb 2011      Member Level: Silver     Points : 2  (Rs 1)    Voting Score: 0


Physical Address and Logical address difference:-

* The physical address is the address which cannot be changed or assigned by user whereas The logical address is address which can easily assign by user.

* Example of physical address is MAC address & Example of logical address is I.P address

* Best Example of physical address is man & example of logical address is his name

Author: Bhaswar    11 Feb 2011      Member Level: Silver     Points : 7  (Rs 6)    Voting Score: 0

To understand the differences between these two addresses we first have to know what these addresses are and what they do .

Physical address : It is an address of a memory location . When some data is stored in that memory location that data is said to be in that physical address .

Logical address : It is the address that the CPU assigns to a piece of data and can be mapped to the actual physical address of the data by certain mapping algorithms .

Suppose for example a variable is stored in the memory location #F000(physical). The logical address for this variable , say , is 1500 . So whenever a process tries to access this variable it tries to access the logical address 1500 . In the mapping scheme 1500 is pre-mapped to the physical address #F000 . Hence a query with the logical address returns the value from the physical address successfully .

Why logical and physical address levels are used :
There are some reasons behind the concept of this two level addressing . Memory allocation is a tricky business and many efficient memory allocation algorithms result in inconsistent and fractioned allocations so two pieces of data which should be placed together logically but due to memory optimization they have to be placed in remote corners of the available memory . In that case storing the addresses in the processors while executing
relevant processes can create considerable overhead . It is better to use logically sequenced addresses in the processor and map them to the physical counterparts elsewhere .

So that's how logical and physical addresses are different and how they work . Hope you found them useful .

Author: SDN    13 Feb 2011      Member Level: Silver     Points : 8  (Rs 8)    Voting Score: 0

Hello friends, let us see the difference in detail.

Physical Address:

# It is also called as MAC address or Ethernet Address or Layer 2 address.
# This address is burnt in the network Adapter called NIC card.
# This is a 48 bit address represented in hexadecimal format.
# To find known MAC to unknown IP address we need a protocol called RARP-Reverse Address Resolution Protocol.
# This address is used inside LAN networks i.e within a single network.
# Example MAC address: 00-0d-65-ac-50-7f

Logical Address:

# It is also called as Network address or layer 3 address.
# It is a 32 bit address represented in 4 octets.
# This address is used when two or more networks communicate with each other.
# To find unknown IP from MAC address we need a protocol called ARP-Address Resolution Protocol.
# This address has two components: Network part and Host part.
# Example IP address: 192.168.1.10

so we discussed about the differences between them. For every networking devices to communicate these addresses are necessary. They are inter-related and works in different layers of the OSI model to deliver the data from source to destination.

I hope my answer is clear and straight to the point. Thank you.


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